1. Field of the Invention
The present invention relates to a method and system (apparatus) for recording a digital audio signal and a digital video signal, more particularly relates to a digital audio and video signal recording method and apparatus for arranging into blocks the same channel of digital audio signals and recording them in a direction orthogonal to the helical (inclined) tracks of the recording medium and a recording medium on which audio signals are recorded in this way.
2. Description of the Related Art
In a system for recording and reproducing analog video signals and analog audio signals (analog type VTR), the video signals are recorded on the helical tracks of a magnetic tape and the audio signals are recorded at the edges running along the longitudinal direction of the magnetic tape at the areas outward from where the video signals are recorded.
Also, in a system for recording and reproducing digital video signals and digital audio signals on a magnetic tape (digital VTR), for example, in Japanese Unexamined Patent Publication (Kokai) No. 56-56075, it has been proposed to record the audio signals on the helical tracks with the same orientation as the video signals from the viewpoint of the advantages of the prevention of loss of audio signals when scratches etc. occur in the longitudinal direction of the magnetic tape, the ability to record and reproduce by the same rotary magnetic head, etc.
Further, for example, in Japanese Unexamined Patent Publication (Kokai) No. 58-188304, it has been proposed to change the recording positions of different channels of audio signals with the aim of rescuing "dropouts" at the time of reproduction when recording a plurality of channels of audio signals on the helical tracks of a magnetic tape.
Still further, for example, in Japanese Unexamined Patent Publication (Kokai) No. 58-188305, a so-called method of "H-arrangement" has been proposed to record a plurality of different types of information on helical tracks in separate zones and to record information recorded in a plurality of related adjoining tracks so that their recording positions are aligned on a line orthogonal to the direction of extension of the tracks so that when erasing information recorded on a certain helical track by an erasure use rotary magnetic head at the time of editing etc., it is possible to prevent information recorded on tracks adjoining the erased helical track from being erased and, further, it is possible to prevent the length of the guard-band from becoming longer.
None of these recording methods is intended to record a plurality of channels of audio signals block by block. Further, none of the above-mentioned recording methods are intended for high density recording such as "high vision (or "high-definition")" systems or for high degree error correction.
FIG. 1 is a view showing, for example, the recording format of digital audio signals and digital video signals of the D1 format defined by CCIR recommendation 657. This example of the format is of the H-arrangement. In this example, the audio signals are recorded at the center portion of the helical tracks and video signals are recorded at the two sides. Further, the recording area is decided on for each channel and consideration is given to enable independent editing for each channel. When the audio signal is rewritten, first, data recorded on tracks to be rewritten are erased by an erasure head, and new data are written on those tracks. In the D1 format, a guard-band is provided between tracks, so it is possible to erase audio signals on desired channels without deleting data on adjoining channels.
High density recording on magnetic tapes is being experimented with as represented by "high vision" systems. In such cases, generally use is made of azimuth recording with no guard-bands (guard-band-less azimuth recording).
FIG. 2 is a view of the format of guard-band-less azimuth recording. FIG. 2A is a view of the recording positions of video signals VIDEO and audio signals AUDIO recorded on the magnetic tape, while FIG. 2B is a view the write processing timing of 8 tracks of audio signals AUDIO and video signals VIDEO before recording. One field is comprised of 16 tracks, but here only 8 tracks are illustrated.
As illustrated in FIG. 2A, the 8 tracks of audio signals AUDIO are recorded at the center of the helical tracks of the magnetic tape. As illustrated in FIG. 2B, the video signals VIDEO and audio signals AUDIO recorded on the tracks are comprised of the front video signals VIDEO-P, the audio signals AUDIO, and the back video signals VIDEO-S. The different tracks of audio signals AUDIO are recorded on the magnetic tape with certain phase differences between them.
When using the D1 audio signal recording format for the guard-band-less azimuth recording, a problem arises during rewriting of a helical track of audio signals, often performed on professional-use VTR's, namely, a partial erasure of the audio signal data recorded on the adjoining helical tracks by the erasure head. The reason is that, in general, the erasure head is set wider than the recording head so as not to allow any data meant to be erased to remain. So the erasure head scans even the adjoining tracks during erasure and part of the audio signal data recorded on the adjoining tracks ends up being erased, that is, narrowing of the adjoining tracks occurs. In addition, during cross (mutual) editing, track deviation also occurs, so unavoidably part of the audio signals recorded on the adjoining tracks end up being erased.
The above-mentioned problem becomes particularly remarkable in the case of a professional-use digital VTR for high density recording where the track widths and pitch are much narrower (narrow-tracks), in particular, "high vision" VTR's.